During the coming year the study of the evolution of modifier genes will be continued, both the general problem and the analysis of special cases of importance. Professors Karlin and McGregor also intend to investigate stochastic modifier models, one purpose of which will be to compare the effect on modifiers exerted by drift with that exerted by secondary selection. It is expected that considerable effort will be devoted to polygenic inheritance models and generally inheritance of quantitative traits. Professors Karlin and McGregor will begin an intensive study of artificial selection models with the objective to gain better insight into the effects of epistasis. Professor Feldman will investigate test of the neutrality hypothesis based on polygenic models. Professors Cavalli and Feldman will continue work on cultural transmission. Further analyses of the correlation between relatives will be carried out, generalizing the one gene model to a polygenic model. The type of relatives to be considered will be extended (e.g. correlation between adoptive sibs) and the type of cultural transmission considered will be extended. Professor Cavalli will study the effect of selective migration between groups for a trait with cultural and/or mendelian transmission. Professor Cavalli assisted by Dr. A. Piazza and others will devote considerable effort to analysis of the HLA data.